A conventional document copying machine is provided with document scanner means for scanning an original sheet placed on a window. In conventional electrophotographic apparatus, the original sheet is exposed by suitable lighting, the reflected light being projected on to a photoconductive belt or drum to form a charge image thereon. A toner image then formed thereon is then transferred to and fixed on a copy sheet. Scanning can be achieved either by means of a moving original sheet, by movement of the window, or by scanning the original sheet by means of an opto-mechanical system with movable reflectors.
In digital document copying machines, photoelectric converters such as CCDs also form part of the document scanner means. In this case the reflected light of an original sheet is projected strip-wise on a row of photoelectric elements. These then generate image signals which are an indication of the quantity of light incident thereon. Such image signals can then be used to expose a photoelectric medium by laser scanning or LED exposure.
U.S. Pat. No. 4,666,287 describes a first embodiment of document scanner means wherein an original can be placed on a window with a transparent part between which the original sheet can be placed with the information page face upwards. The original is fixed on the window by a clip. This window and clip assembly is movable over a transparent window of an analogue document copying machine. In this case the term "analogue" denotes a direct exposure of a photoconductor by the reflected light. The advantage of a movable window is its simplicity. A disadvantage, however, is the need to keep the original sheet properly in position during the movement of the window. Particularly in the case of bound documents, the clip required for this purpose may involve the risk of damaging the document. The patent then proposes to replace these relatively simple scanner means with a movable window in such cases, by more complex scanner means with an immovable window. For this purpose, in a second embodiment, the entire assembly of the movable window and clip of the document copying machine is removed and replaced by scanner means having an immovable window. By moving a linear reflector over the original sheet in combination with a second reflector moving in the opposite direction, a projection of the original sheet through the transparent window is obtained on the photoconductor of the document copying machine via a lens system.
Since the original sheet no longer has to be moved, it consequently no longer needs to be clipped so firmly. This reduces the risk of damage to a bound document.
Another problem is that in scanner means in which a bound document is placed with the information page face up, the document always has to be turned over to be able to turn to the next page of the document. This is a complicated procedure. In addition with bound documents there is the distortion which occurs when a thick document is placed opened on a flat window. Defocusing and distortion occur in the image formation. There is also a loss of light and reflection due to incomplete contact between a flat window and flat clip.
The U.S. Pat. No. 4,666,287 describes a third embodiment of scanner means in which a bound document is held against a V-shaped window with the information page face up and partially opened. A reflector is then moved parallel to one of the two sides of the V-shaped window. Since a bound document now no longer has to be opened into one plane, there is less risk of distortion of the bound document. The disadvantage, however, is that the construction now becomes complex, having two sides of a window at an angle, and hence expensive, while the document copying machine is now unsuitable or much less suitable for copying loose original sheets since the original scanner means have been removed.
Precautions also have to be taken to enable the original scanner means to be readily removed. This in turn involves extra steps and limitations in the construction of the original scanner means. This means that with existing document copying machines, it is not possible to mount the above-described alternative document scanner means. Replacement is even impossible particularly in the case of scanner means integrated in a document copying machine in the housing beneath the window. Making adjustments to document copying machines involves extra unnecessary expense for those users who do not require extra facilities for copying bound documents. More often than not, it is a restricted small group of specific users, such as libraries, who have a specific requirement for facilities for copying books. This, however, results in a general increase in price if the document copying machines are made suitable for all users in order to replace the existing document scanner means by alternative scanner means. A limited series of adapted document copying machines also involves extra costs in terms of manufacturing, because of the small scale of production involved. In addition, there are logistical and servicing disadvantages in marketing two different constructions of document copying machines, one of which is suitable for replacement with extra document scanner means and the other unsuitable for this purpose.